1. Field of the Invention
This invention relates to an automatic lens meter for automatically measuring the optical refractive power of spectacle lenses or the like.
2. Description of the Prior Art
A light beam detecting type of lens meter is known. This lens meter utilizes the fact that measurement of the deviated path within a preselected area of excursion is typically equated to various powers of the suspect optical system in sphere, cylinder, cylinder axis and prism. For example, a lens meter with automated readout disclosed in U.S. Pat. No. 4,180,325 is a means of measurement of deviated paths and includes a moving boundary locus with edges of distinctly different shape placed to intercept and occult said deflected beam in a known plane within the area of excursion at a distance from the suspect optical system. The moving boundary locus is arranged for movement along a predetermined path at a velocity within the known plane. The boundary locus includes a first substantially transparent portion, a second substantially opaque portion, and at least two boundaries between the opaque and transparent portions.
However, this lens meter has required a moving boundary locus having a special pattern and accordingly has been complicated in construction.